IDENTIFICATION OF AN ERYTHROCYTE BINDING PEPTIDE FROM THE ERYTHROCYTEBINDING ANTIGEN, EBA-175, WHICH BLOCKS PARASITE MULTIPLICATION AND INDUCES PEPTIDE-BLOCKING ANTIBODIES

A biotinylated peptide covering a sequence of 21 amino acids (aa) from the erythrocyte binding antigen (EBA-175) of Plasmodium falciparum bo und to human glycophorin A, an erythrocyte receptor for merozoites, as demonstrated by enzyme-linked immunosorbent assay (ELISA) and to eryt hrocytes as demonstrated by flow cytometry analysis. The peptide, EBA( aa1076-96), also bound to desialylated glycophorin A and glycophorin B when tested by ELISA, The peptide blocked parasite multiplication in vitro. The glycophorin A binding sequence was further delineated to a 12-aa sequence, EBA(aa1085-96), by testing the binding of a range of t runcated peptides to immobilized glycophorin A. Our data indicate that EBA(aa1085-96) is part of a ligand on the merozoite for binding to er ythrocyte receptors. This binding suggests that the EBA(aa1085-96) pep tide is involved in a second binding step, independent of sialic acid, Antibody recognition of this peptide sequence may protect against mer ozoite invasion, but only a small proportion of sera from adults from different areas of malaria transmission showed antibody reactivities t o the EBA(aa1076-96! peptide, indicating that this sequence is only we akly immunogenic during P. falciparum infections in humans. However, T anzanian children with acute clinical malaria showed high immunoglobul in G reactivity to the EBA(aa1076-96) peptide compared to children wit h asymptomatic P, falciparum infections, The EBA(aa1076-96) peptide se quence from EBA-175 induced antibody formation in mice after conjugati on of the peptide with purified protein derivative, These murine sera inhibited EBA(aa1076-96) peptide binding to glycophorin A.